This invention relates to a process for treating a plurality of streams containing chlorosilicon compounds. More specifically this invention relates to a process for treating a plurality of streams containing chlorosilicon compounds to obtain a solid siloxane material or gel that is easily handleable in further processing steps, shipment, or disposal operations.
A wide variety of commercial silicone polymers are produced by the hydrolysis of a few basic chlorosilanes. Also, pure silicon metal useful in the fabrication of semiconductor devices is made from the reduction of certain chlorosilanes. These important chlorosilane monomers are produced by processes that also yield minor amounts of by-products. For example, methylchlorosilanes are obtained from the reaction of methyl chloride with silicon by what is commonly called the "direct process" method; and chlorosilanes are produced from the reaction of silicon metal with hydrogen chloride. Because of the commercial importance of these and other processes for producing chlorosilanes, large amounts of by-product streams are generated. Additionally, other minor waste streams are produced in a commercial silicone plant. These minor waste streams include, for example, distillation residues, contaminated wash solvents, reaction residues from production of intermediates, and off-specification material.
The eventual disposition of these by-product and waste streams has become a significant problem as the production volume of silicone polymers has increased. Both the increased volume of the waste streams and the complexity and variability of the individual streams contribute to the waste disposal problems of a commercial silicone operation.
An approach to the problems of waste disposal was disclosed in U.S. Pat. No. 4,221,691, issued Sept. 9, 1980 to Danielson and Ingebrigtson, which is hereby incorporated in its entirety by reference. Danielson et al. taught that the addition of a relatively small amount of a hydrocarbon oil to a polyfunctional chlorosilicon composition prior to hydrolysis significantly improves the handling characteristics of the siloxane gel that is obtained. The term "polyfunctional chlorosilicon composition" was defined as "compositions containing a major proportion of chlorosilicon compounds with at least 3 chlorine radicals bonded to silicon per molecule." Therefore, the method of Danielson et al. could not be used to successfully hydrolyze many of the by-product or waste streams of a commercial silicone plant to obtain a handleable gel since many of these streams may not contain sufficient polyfunctional chlorosilicon compounds. Furthermore, the use of the hydrocarbon oil of Danielson et al. represents an additional expense in the waste treatment process. Also, the presence of the added hydrocarbon oil in the siloxane gel may present additional obstacles in the eventual disposition of the produced siloxane gel especially in the present era of heightened environmental concerns.
It is an object of this present invention to provide a process for treating a plurality of by-product and/or waste streams containing chlorosilicon compounds to produce a siloxane gel that is easily handleable in further processing steps, shipment or disposal. Another object of this invention is to provide a process by which the diverse by-product and/or waste streams of a commercial silicone plant can be economically hydrolyzed to greatly reduce the chlorine content prior to disposal. Still another object of the present invention is to provide a method of treating by-product and/or waste chlorosilicon streams whereby hydrogen chloride may be recovered. Still other objects of this invention will be known to those skilled in the art upon consideration of this specification.